A known image forming apparatus performs an image adjustment to prevent an occurrence of positional deviation of an image and a deviation of print density. In the image adjustment, for example, a mark for positional deviation adjustment (e.g., a registration pattern) is formed onto a conveyor member (e.g., a sheet conveyor belt) by each color of the image forming apparatus and an amount of deviation between registration patterns of reference colors and registration pattern of test subject colors is determined. Based on a correction value specified by the deviation amount, the positional deviation of images formed in the test subject colors is corrected.
Conventionally, the mark for image adjustment is formed on a belt after cleaning of the belt. After the mark is formed, the mark is measured and an image is adjusted.